Method of adhesively bonding foldable board



May 16, 1961 K. c. GoBALET 2,984,598

METHOD oF ADHESIVELY BONDING FOLDABLE BOARD IN VEN TOR. Kennef/l C/deGraba/ef M ATToRNEYs May 16, 1951 K` c. GOBALET 2,984,598

METHOD oF ADHEsIvELY BONDING FOLDABLE BOARD Filed Jan. 7, 1958 4Sheets-Sheet 2;

#um 47. leu/MM IMI ATToR/vfm May 16, 1961 K. c. GOBALET 2,984,598

METHOD OF ADHESIVELY BONDING FOLDABLE BOARD Filed Jan. 7, 1958 4Sheets-Sheet 3 [N V EN TOR. a /fefme fh CQ/ae Gobalez A TTORNEYS May 16,1961 K. c. GoBALx-:T

METHOD oF ADHESIVELY BONDING FOLDABLE BOARD Filed Jan. '1, 195s 4Sheets-Sheet 4 INVENOR. Kenne/v C75/de Goba/ez A 7'7' ORNE YS UnitedStates Patent O i METHOD OF ADHESIVELY BONDING FOLDABLE BOARD KennethClyde Gobalet, Redwood City, Calif., assignor to Baljak Corporation,Wilmington, Del., a corporation of Delaware Filed Jan. 7, 1958, Ser. No.707,601

9 Claims. (Cl. 154-120) This invention relates to the art of adhesivelybonding overlapping areas of foldable board, such as paperboard, boxboard, or other foldable sheet material, during the shaping of a boxblank into hollow box form or during the closing and sealing of boxesafter filling.

In the folding box industry the terms gluing and gluing machine areoften used in a generic sense, even though the adhesive which isemployed is not actually glue in the strict sense of the word. Glue isdefined in the Dictionary of Paper (American Paper and Pulp Association,New York, 1940), as Impure gelatine obtained from bones, hides, tannerywaste, iish heads, etc. by boiling with Water, rfiltering,concentrating, and drying. The adhesive employed in a gluing machine isfrequently a synthetic adhesive composition, such as a hot-meltcomposition, or compositions of a specific thermoplastic nature.

In this description the term gluing will sometimes be used in itsbroader sense in keeping with the custom in the industry.

IIn the conventional forming, as well as in the sealing, of boxes anadhesive applicator first applies adhesive to the board, whereafter theboard areas which are to be bonded are brought into contact. The gluejoint then moves into the so-called pressure section of the machine inwhich the joint is maintained under pressure for a time suiiicient topermit the adhesive to set. The higher the output rate of the gluing orsealing machine, the longer the pressure section of the machine must bein order to maintain the joint under pressure for the required number ofseconds. The pressure section of a high output machine thereforeoccupies a considerable amount of oor space.

Where glue or synthetic adhesives are applied in a dilute state, thesetting of the adhesive involves the absorption or dissipation of thesolvent.

Thermoplastic adhesives employed for heat sealing require dissipation ofthe sealing heat. For this purpose cooling elements are often installedin the pressure section to accelerate the setting of thermoplasticadhesives.

Particular problems are encountered in the sealing of boxes containingfoods about to be frozen. Frozen products are generally packaged inboxes made from a waxcoated stock, the most common coating beingparafline wax, or compositions in which paraiiine forms a constituent.Wax-coated board, unlike uncoated board, has a very limited ability toabsorb moisture. Moisture left in the adhesive bond freezes duringsubsequent refrigeration of the box and contents, with the danger ofgreatly weakening or destroying the seal.

The present invention offers particular advantages when applied towax-coated board, particularly parafiine coated board.

According to the present invention an instant or contact-type bond isformed which after an initial and brief application of pressure requiresno continued application of pressure, thus eliminating the need for anextended pressure section in the gluing or sealing machine. The

2,984,598 Patented May 16, 1961 ICC` bond produced is moisture free forall practical purposes and remains secure and reliable at lowrefrigerating temperatures of the order of zero degrees F. as well as athigh daytime temperatures of the order of degrees F.

The various objects, features and advantages of this invention Iwillappear more fully from the detailed description which followsaccompanied by drawings showing, for the purpose of illustration, a formof device for practicing the invention. 'Ihe invention :also resides incertain new and original steps, sequence of steps, as well as featuresof construction and combination of elements hereinafter set forth andclaimed.

Although the characteristic features of this invention which arebelieved to be novel will be particularly pointed out in the claimsappended hereto, the invention itself, its objects and advantages, andthe manner in which it may be carried out, may be better understood byreferring to the following description taken in connection with theaccompanying drawings forming a part of it, in which:

Figure 1 is a diagrammatic plan View of a machine for carrying out thenovel method;

Figure 2 is a perspective view of the machine of Figure l;

Figure 3 is a perspective view of the central portion of the machine ofFigure 2, including the applicator of the bonding composition;

Figure 4 is a diagrammatic elevational view of the applicator of Figure3;

Figure 5 is a diagrammatic perspective view of the composition transferportion of the machine;

Figure 6 is a diagrammatic plan view of the portion of the machinewithin which the composition is converted into a highly tackycontact-type of adhesive;

Figure 7 is a diagrammatic end view of the machine portion shown inFigure 6;

Figure 8 is a diagrammatic perspective view of the sealing portion ofthe machine;

Figure 9 is a perspective view of the end portion of the adhesiveconverting section and of the sealing mechanism; and

Figure 10 is a reproduction of a test strip of board to which aqueousmedium was applied at certain temperatures within the range from 70 .to250 degrees F.

In the following description and in the claims various details will beidentified by specific names for convenience. The names, however, areintended to be generic in their application. Corresponding referencecharacters refer to corresponding parts in the several figures of thedrawings.

The drawings accompanying, and forming part of, this specificationdisclose certain specific details of the invention for the purpose ofexplanation of its broader aspects, but it is understood that thedetails may be modified in various respects without departure from theprinciples of the invention. The invention may also be applied withgreat advantage to the bonding of plain, unwaxed board, or to boardwhich was dewaxed by a separate process.

For the purpose of explanation of the features and advantages of theinvention it will be assumed that the specific object is the bonding ofa front flap depending from the cover panel of a hinge cover box to thefront wall of the box which the flap overlies, and it will be assumedthat the box is constructed from a blank of waxed stock. Waxed board isdiflicult to bond adhesively and the diculties are increased by arequirement of completing the bond at a high rate of speed and within arelatively short length of box travel.

Once the details and features of the new method are appreciated, it willreadily be seen that the invention is equally applicable to conditionspresenting lesser 3 problems, such as the bonding of panels or flaps ofplain, unwaxed board.

The sealing machine 1'1 comprises a conveyor 12 provided with lugs 13for `moving boxes 14 from an infeed end 15 'to adischarge end 16 ofthemachine.

The illustrated machine was specifically designed for 4handling waxedboard and comprises, for this reason, an initial heating and dewaxingsection 1'7 which precedes an adhesive applicator section 18. A furthersection 19 follows which converts the initially lessentially non-tackybonding composition into a composition of high tackiness ofthe instantlybonding vor contact adhesive type. In a closing section 20 the adhesivecoated blank portions 'are pressed into bonding engagement on contact.

Referring to Figure 2, the box 14 has a cover panel 21 articulated Ytothe back wall YpanellZ along a cover hinge line 23. The cover panel isprovided with side .flaps 24 and 25 and a frontap 26 articulated to thecover panel along fold lines 27, 28 and 29, respectively. The box is atypical frozenfood box measuring %x513x 1%6.

For the purpose of this description only the bonding of the front flap26 to the front wall 30 (Figure 8) of the box will be considered, itbeing understood that the side flaps 24 and 25 may be bonded .to therespective side wall panels in a corresponding manner.

The sealing and closing machine 11 comprises a top rail 31 which engagesthe initially upright cover panel of the box and folds it, in aconventional manner, into the position in which it is shown in Figure 2.In this position the flaps 24, 25 and 26 lie in the same plane as thecover panel.

All of the inside as well as outside surfaces of the box entering themachine are coated with a moisture proofing wax coating consistingessentially of paraine wax applied to the board in a conventionalmanner.

Asthe box is advanced by the conveyor 12 in the direction away from theobserver (Figure 2), the box rst passes through the heating and dewaxingsection 17 equipped with a heating unit 32 having two major box panelengaging surfaces 33 and 34. Surface 33 is upright and bears against thefront wall panel 30 of the box. The surface 34 extends at a slightdownward slant and is designed to bear against the undersurface of thebox flap 26. A blade 35 is urged against the surface 34 by springs 36and 37 and bears against the top surface of the flap 26 to press thefront flap wall against the slanted surface 34 of the heating unit. Thedegree of downward slant is small in order to avoid lessening, at thisstation, of the fold resistance or fight of the board at the flap hingeline, for reasons which will appear later.

The leading portion of the heating unit is flared and resemblesapproximately the bow of a boat turned upside down as shown at 38. Theleading end of the blade 35 is up, as seen at 39. The heating unitcomprises four resistance heating elements of 1000 watts each, a portionof one element being visible at 40, the heating controls for theelements being enclosed in a control box 41.

When the box passes through the heating section the board surfaces to bebonded are dewaxed by heat. The heating step serves two major purposes.Firstly, it removes wax by driving a portion of the wax originallydeposited on the board surface into the board itself, another portionbeing converted into vapor which escapes. The vapor also includes somewater vapor, since the board normally contains a low percentage ofmoisture. The development and escape of vapor causes the board to fluffup slightly with a resulting increase in its surface porosity. This ishighly desirable'and prepares the board for the subsequent applicationof the bonding composition.

The output of the heating unit must be sufficient to attain the requiredboard temperature, the principal determining factor being the totalweight of'board to be heated per second. More particularly, the heatoutput u ture of these resins are disclosed in textbooks.

is determined on the basis of the caliper of the board, the rate oftravel of the conveyor, the thermal properties of the coating material,the moisture content of the board and the area of board to be heated.

In the case of the specific frozen food box, which may serve as anexample, parafiined board of 15 point caliper .was used, and the boxeswere advanced at the rate of .16 'inches per second. The temperatureofthe heating unit was 375 degrees F. resulting in heating of the boardto a vtemperature of about 250 degrees F. during travel of the box pastthe unit which required 1.24 seconds.

In the event plain, unwaxed board is used, or board which was previouslydewaxed by any of the various conventional dewaxing procedures, it isstill preferred to pass the board through the heating section in orderto take advantage of its second major purpose, which is to heat theboard immediately prior to the application of the bonding composition.

It was discovered that the receptivity of the board to the composition,particularly the penetration of the fluid -composition into the board,is considerably enhanced by application of the adhesive to a heatedrather than a cold'board surface. The reasons for this phenomenon appearcomplex and various theories may be advanced to explain it. Because ofthe complexity it is preferred to record the results of tests from whichthe merits of the heating procedure are directly apparent.

Figure l0 is a reproduction of a test strip of previously dewaxed boardto which liquid composition was applied at temperatures of 70, 80, 100,120, 137, 145, 158, 165, 178, 190, 200, 205, 220, 230 and 250 degrees F.In order to make the receptivity of the board to the applied compositionvisible, dye was added, so that the quantity of absorbed liquid appearsas varying degrees of discoloration. In each instance liquid of roomtemperature was applied with a saturated brush to the board heated tothe temperature indicated.

It is readily apparent that the receptivity of the board to liquidcomposition is low below 145 degrees F. 145 degrees marks a criticalpoint in the temperature range as exemplified by the much heavierabsorption at 158 degrees. The test series was concluded by a final testconducted at 70 degrees F. to obtain corroborating readings at thebeginning and at the end of the entire series. 'Ihe almost identicalappearance of the two 70 degree test strips indicates that the board wasnot altered by the heat treatment incidental to the tests.

Adhesive composition is applied to waxed board having a temperature inexcess of 212 degrees F., preferably approximately 250 degrees, while itis preferred to raise the temperature of plain, unwaxed board to` atemperature in excess of 145 degrees F. for application of thecomposition.

After the box leaves the heating section 17 its front flap 26 isflattened out and passed over an adhesive applicator shown in Figure 3as being an applicator wheel 42 having peripheral raised applicatorareas 43. As shown in greater detail in Figure 4, the wheel 42 issupplied adhesive composition 44 from a receptacle 45 via a transfer'roll 46 fitted with a doctor blade 47. A film of liquid composition ofcontrolled thickness is thus putV on the applicator areas l43 forsubsequent application to the underside of a flap 26. Guide rails 48, 49and 50 insure proper contact between the panel 21 and flap 26 and theapplicator wheel 42, respectively.

The adhesive composition is essentially an aqueous emulsion of theconsistency of heavy cream. The adhesive constituent is in solid formand is a finely divided thermoplastic resin. For test purposes a wellknown and commercially available polyvinyl acetate resin known to thetrade as Du Pont Elvacet ##900 was used. Competitive products are knownunder the trade names Polyco, Vinylite and Gelva.

The chemical composition and processes of manufac- Chemic als ofCommerce by Snell and Snell, Van Nostrand and Company, lNew `York, 1952,page 530, lists polyvinyl acetate resins by trade names and identitiesthese as being catalyzed reaction products of acetylene and acetic acid.These resins are commercially available as solution and stable emulsionsof varying viscosity and particle slze.

The present invention employs these resins in their emulsion form. Theemulsion is of rather low tackiness as distinguished from the solutionform which is highly tacky. t

The emulsion used during the tests consisted of 55% `solids and 45%aqueous medium by weight. This is a favorable proportion. By way ofcomparison a solvent such as methyl ethyl ketone mixed with polyvinylacetate particles in the ratio of 55% solids to 45% liquid will justabout swell the solids, but not produce a readily liowable liquid.

Vinylite is produced by polymerizing a mixture of vinyl acetate andvinyl chloride, as is well known in the art. Rubber latex is alsosuitable as an adhesive component.-

The general requirement for the adhesive is that it should be applicablein an emulsion state and adapted to be converted into a state of hightackiness by a subsequent brief heat treatment, as will be described.

In view of the large number of existing synthetic resins and the rapiddevelopment of new and improved resin compositions, it will be helpfulto specify the characteristics on the basis of which suitable materialsmay be selected.

The synthetic resin should be substantially insoluble in water andcapable of forming a stable aqueous emulsion. Its color shouldpreferably be light and it should be non-toxic, if used for sealing foodcartons. It should preferably exhibit low specific heat characteristicsso as to heat and cool rapidly and its physical characteristics shouldbe as follows: It should be substantially leathery in the range of minus40 to plus 180 degrees F., it should be rubbery in the range of 180 to212 degrees. It should have a melting point at or near the boiling pointof water and it should be fluid above the boiling point of water. Theaforementioned composition Elvacet #80-900 meets these specificationsand forms an excellent sealing composition.

The securest bond is formed between adhesive coated areas on both thebox panels which are to be secured together. While it is feasible toapply adhesive composition to the front wall of the box directly bymeans of an adhesive applicator, as previously described, it ispreferred to transfer a portion of the composition applied to the tlap26 to the wall panel 30.

` A preferred mode of accomplishing this is illustrated in Figure 5. Theflap 26 is engaged by a rail 51 which slopes downwardly and towards thebox body, thus swinging the flap 26 against the wall panel 30 as the box14 advances. A roller 52 of resilient construction presses the flap 26rrnly against the underlying wall panel 30, thus transferring a portionof the adhesive previously applied to the underside of the ap 26 to thewall panel 30. The back wall of the box 14 is supported by a Wall orblade 58. The pattern of the adhesive on the Hap bears the referencecharacter a and the pattern of the adhesive applied to the wall panel 30by way of transfer is identified by the reference character a'.

As previously mentioned, the adhesive composition at this stage exhibitsa rather low degree of tackiness, insuliicient to hold the ap 26 downafter the box moves beyond the roller 52. The ilap 26 thus springs awayunder the action of the inherent fold resistance or iight of the stockat the fold line 29 and assumes the position shown in Figure 5.

By subsequent treatment step the adhesive composition is now convertedfrom its substantially non-tacky state into a state of high tackinesslThe conversion is carried out in the baking or heating section 19 of themachine. It comprises a series of tubular heat applicators, preferablyinthe form of quartz lamps, three 1,000 watt quartz lamps of typeT3-l000 being employed in the illustrated machine. The lamps 53 aremounted in line in the focal line of a reector S4 having an upwardextension 55 for the purpose of reducing heat loss through and beyondthe flap 26 of the carton 14.

The heat is sufficient to evaporate the aqueous medium of thecomposition, during which phase of the treatment the temperature of thecomposition coating remains at approximately 212 degrees F. As soon asthe aqueous medium is evaporated, the temperature of the compositiondeposit rises sharply and causes the previously separated and dispersedresin particles to fuse. The temperature at which this occurs depends onthe characteristics of the resin. -In the case of Du Pont Elvacet #-900having a melting point between 203 and 212 degrees F. according toinformation by the manufacturer, the fusing occurs at a temperature ofless than 325 degrees F.

The temperature is effectively controlled by the duration of exposure ofthe composition to the heat radiated by the quartz lamps, the time being2.75 seconds in the specific example.

When the box passes out of the baking section 19 its composition coatedsurfaces are highly tacky and need only be brought into brief contact toform an instant bond.

The bond is suiciently strong to permit normal handling of the boxesleaving the machine. The bond becomes even stronger as the joint coolsto room temperature. 'If the bond is forcibly broken shortly after thebox passes the pressure rollers 57, the adhesive forms tough, rubberystrings between the forcibly separated surfaces. The force required toseparate the sealed surfaces is considerable and increases as the boardcools to room temperature.

Referring to Figure 8, the aps 26 are caught under a downwardly andinwardly sloping rail 56 which swings the `liap against the wall panel30. A series of four resilient pressure rollers 57 is employed to pressthe ilap 26 into firm contact with the wall. Thereafter the box isdischarged, completely and securely sealed and ready for refrigerationin the event the box contents are to be frozen. There is no problem offreezing of a liquid component of the composition, nor is there a dangerof entrapment of volatile material in the adhesive joint proper. Thebond is secure at freezing temperatures at which foods are frozen andstored and does not become brittle. It is equally secure at tropicaltemperatures.

Specific dimensional and time data readily show the advantages of theinventive method. The specific machine shown in the drawings had anoverall length of the conveyor track of 132 inches. Of the total, 20inches comprise the preheater which, in the present example, also servesas a dewaxer. The adhesive application section proper occupied 15inches, plus an additional 22 inches for transfer of the composition inthe described manner, a total of 57 inches. The adhesive conversionsection occupied 44 inches and a closing section was 3l inches long.

The preheating and dewaxing step required 1.24 seconds. The travel pastthe adhesive applicator required 0.94 second and the transfer of theadhesive required an additional 1.38 seconds. The adhesive was convertedyfrom its essentially non-tacky state to a highly tacky state within2.75 seconds and bond was completed within the closing section in aperiod of 1.94 seconds. The total time required was 8.25V seconds, anaccomplishment which is believed to be unequalled in the art ofadhesively sealing waved cartons.

What is claimed is:

l. The method of securing together in face-to-face relationshipoverlapping areas of two surfaces of board of a folding box blank, themethod comprising, the steps of applying to the areas to be adhered anaqueous emulsionof a thermoplastic adhesive; then heating the appliedadhesive on the board to a temperature above the boiling point of waterto a point sufficient to melt the adhesive component, thereby convertingthe adhesive component from its divided emulsion state of low tackinessinto a contact-type adhesive of high tackiness; and then pressing theadhesive coated areas together, whereby an instantaneous contact-typebond is formed.

2. The method of securing together in face-to-face relationshipoverlapping areas of two surfaces of board of a folding box blank, themethod comprising, the steps of first heating Vthe board areas to atemperature in excess of 145 degrees F.; then applying to the areas anaqueous emulsion of a thermoplastic adhesive; then heating the appliedadhesive on the board to a temperature above the boiling point of waterto a point sucient to fuse the adhesive component, thereby convertingthe adhesive component from its divided emulsion state of low tackinessinto a contact-type adhesive of high tackiness; and then pressing theadhesive coated areas together, whereby an instantaneous contact-typebond is formed.

3. The method of securing together in face-to-face relationship areas oftwo surfaces of board of a folding box blank, the method comprising, thesteps of applying to one of said areas an aqueous emulsion of athermoplastic adhesive; then pressing saidfadhesive coated one areaagainst a second area of a surface to which said rst area is to beadhered, thereby transferring adhesive emulsion from said one area tosaid second area; then separating said two areas; then applying heat tothe adhesive on said rst and on said second area, while said areas areseparated, to raise the temperature of the adhesive above the boilingpoint of water to a point sucient to fuse the adhesive component,thereby converting the adhesive component from its divided emulsionstate of low tackiness into a contact-type adhesive of high tackiness;and then pressing the adhesive coated areas together, whereby aninstantaneous contact-type bond is formed.

4. The method of securing in face-to-face relationship areas of twosurfaces of board of a folding box blank, the method comprising, thesteps of rst heating at least one of the board areas to be adhered to atemperature in excess of 145 degrees F.; then applying to only said onearea an aqueous emulsion of a thermoplastic adhesive; pressing saidadhesive coated one area against a second area of a surface to whichsaid rst area is to be adhered, thereby transferring adhesive emulsionfrom said one area to said second area; then sep- -arating said twoareas; then applying heat to the adhesive on said rst and on said secondarea, while said areas are separted, to raise the temperature of theadhesive above the boiling point of water to a point suflcient to fusethe adhesive component, thereby converting the adhesive component `fromits divided emulsion state of low tackiness into a contact-type adhesiveof high tackiness; and then pressing the adhesive coated areas together,whereby an instantaneous contact-type bond is formed.

5. The method of securing together in face-to-face relationshipoverlapping areas of two surfaces of wax coated board of a folding boxblank, the method comprising, the steps of first moving the board areasto be adhered past, and in contact with, heating surfaces to heat theboard to a temperature in excess of 145 degrees F. and a pointsufficient to dewax the board surface; then applying to the dewaxedsurfaces, while still hot, an aqueous emulsion of a thermoplasticadhesive; then heating the applied adhesive on the board to atemperature above the boiling point of water to a point sufficient tofuse the adhesive component, thereby converting the adhesive componentfrom its divided emulsion state Yof low tackiness into a 'contact-typeadhesive of high tackiness; and then pressing the adhesive coated areastogether, whereby an instantaneous contact-type bond is formed.

6. The method of .securing together in face-to-face relationshipoverlapping areas of two surfaces ofwax coated board of a folding boxblank, the method comprising, the steps of first moving the board areasto vbe adhered past, and in contact with, heating surfaces to heat theboard to a temperature in excess of degrees F. and a point sufficient todewax the board surface; then applying to only one of said areas anaqueous emulsion of a thermoplastic adhesive; pressing said adhesivecoated one area against a second area of a surface to which said firstarea is to be adhered, thereby transferring adhesive emulsion from saidone area to said second area; then separating said two areas; thenapplying heat to the adhesive on said rst and on saidsecond area, whilesaid areas are separated, to rise the temperature of the adhesive abovethe boiling point of water to a point sufficient to fuse the adhesivecomponent, thereby converting the adhesive component from its dividedemulsion state of low tackiness into ya contacttype adhesive of hightackiness; and then pressing the adhesive coated areas together, wherebyan instantaneous contact-type bond s formed.

7. The method of securing together in face-to-face relationshipoverlapping areas of two surfaces of wax coated board of a yfolding boxblank, said areas having been dewaxed and being at a temperature Withinthe range of normal room temperatures, the method comprising, the stepsof rst heating said board areas to a temperature in excess of 145degrees F.; then applying to the areas an aqueous emulsion of athermoplastic adhesive; then heating the applied adhesives on the boardto a temperature above the boiling point of water to a point suflcientto fuse the adhesive component, thereby converting the adhesivecomponent from its divided emulsion state of low tackiness into acontact-type adhesive of high tackiness; and then pressing the adhesivecoated areas together, whereby an instantaneous contacttype bond isformed.

8. The method of securing together in face-to-face relationshipoverlapping areas of two surfaces of wax coated board of a folding boxblank, said areas having been dewaxed and being at a temperature withinthe range of normal room temperatures, the method comprising, the stepsof first heating said board areas to a temperature in excess of 145degrees F.; then Vapplying to only one of said areas an aqueous emulsionof a thermoplastic adhesive; pressing said adhesive coated one areaagainst a second area of a surface to which said first area is to beadhered, thereby transferring adhesive emulsion from said one area tosaid second area; then separating said two areas; then applying heat tothe adhesive on said rst and on said second area, while said areas areseparated, to raise the temperature of the adhesive above the boilingpoint of water to a point su'icient to :fuse the adhesive component,thereby converting the adhesive component from its divided emulsionstate of low tackiness into a contact-type adhesive of high tackiness;and then pressing the adhesive coated areas together, whereby aninstantaneous contact-type bond is formed.

9. The method of securing together in face-to-face relationshipoverlapping areas of two surfaces of. board of a folding box blank, themethod comprising, the steps of applying to at least one of the areas tobe adhered an aqueous emulsion of a thermoplastic adhesive; then heatingthe applied adhesive on the board to a temperature Vsufficient to meltthe adhesive component to cause the adhesive particles of the emulsionto coalesce; and pressing together the two surfaces of board during aperiod following application of the heat, 'whereby an instantaneous bondis formed.

(References on following page) References Cited in the le of this patentUNITED STATES PATENTS Merritt Apr. 30, 1935 Hinrichs May 12, 1936 5Widell Aug. 15, 1939 Bergstein Sept. 23, 1941 Metcalf June 30, 1942 ZinnNov. 20, 1951 10 Berry et al. May 24, 1955 Wittcoff Dec. 27, 1955Wooldrick Oct. 22, 1957 Hermann et al. Oct. 7, 1958 Britton Nov. 18,1958 Nelson Feb. 3, 1959 Phin Feb. 24, 1959 UNITED STATES PATENT @TimeCERTIFICATE 0F CRRECT1CN Patent No., .2,984,598 May 1 1961 Kenneth ClydeGobalet It is hereby certified that error appears in the above numberedpatent requiring correction and that the said Letters Patent should readas lcorrected below.

Column 5v line 73, after "By" insert n a -M column line 71, for "waved"read waxed =fe Signed and sealed this 16th day of January 1962.

(SEAL) Attest:

ERNEST W. SWIDER DAVID L. LA DD Attesting Officer I Commissioner ofPatents

3. THE METHOD OF SECURING TOGETHER IN FACE-TO-FACE RELATIONSHIP AREAS OF TWO SURFACES OF BOARD OF A FOLDING BOX BLANK, THE METHOD COMPRISING, THE STEPS OF APPLYING TO ONE OF SAID AREAS AN AQUEOUS EMULSION OF A THERMOPLASTIC ADHESIVE, THEN PRESSING SAID ADHESIVE COATED ONE AREA AGAINST A SECOND AREA OF A SURFACE TO WHICH SAID FIRST AREA IS TO BE ADHERED, THEREBY TRANSFERRING ADHESIVE EMULSION FROM SAID ONE AREA TO SAID SECOND AREA, THEN SEPARATING SAID TWO AREAS, THEN APPLYING HEAT TO THE ADHESIVE ON SAID FIRST AND ON SAID SECOND AREA, WHILE SAID AREAS ARE SEPARATED, TO RAISE THE TEMPERATURE OF THE ADHESIVE ABOVE THE BOILING POINT OF WATER TO A POINT SUFFICIENT TO FUSE THE ADHESIVE COMPONENT, THEREBY CONVERTING THE ADHESIVE COMPONENT FROM ITS DIVIDED EMULSION STATE OF LOW TACKINESS INTO A CONTACT-TYPE ADHESIVE OF HIGH TACKINESS, AND THEN PRESSING THE ADHESIVE COATED AREAS TOGETHER, WHEREBY AN INSTANTANEOUS CONTACT-TYPE BOND IS FORMED. 